The present invention is directed to a personal alarm which is used to protect valuables or other items provided in an unlit or darkened enclosure of a relatively small area.
The prior art is replete with various devices used to protect valuables provided in an unlit or darkened enclosure having a relatively small area. Typical of these prior art devices are those which are described in U.S. Pat. Nos. 3,909,819 issued to Radford; 3,930,249 issued to Steck et al; 4,063,251 issued to Harsnett; 4,155,077 issued to Rohan et al; 4,242,670 issued to Smith; 4,255,745 to Rohan et al; 4,558,307 issued to van Lidt de Jeude; 4,617,556 issued to Rivera et al; and 4,977,392 issued to Loda.
Generally, these prior art devices are used to protect items stored in lockers provided at work or at athletic clubs, automobile glove compartments, an office drawer, a briefcase, various household or medicine cabinets provided in the home or office, or similar environments.
For example, the patents to Rohan et al describe an apparatus for audibly signalling the opening of a darkened enclosure. The apparatus described in these patents would include a battery powered system comprising a photodetector, a time delay, an oscillator, an amplifier, and a transducer, such as a small loudspeaker. The opening of the darkened enclosure is sensed by the photodetector allowing the time delay circuit to be initiated. The patent to Rivera et al illustrates a photosensitive sound generator which is adapted to be placed in a darkened enclosure. Once the enclosure is opened, a sound transducer, such as a piezoelectric device, will become audible. Additionally, the patent to Smith shows a photosensitive alarm system which produces a signal upon exposure to ambient light for protection of cash drawers, file cabinets and similar darkened enclosures. This system is capable of detecting multiple intrusions, recording the number of intrusions, and providing alarm signals indicative of the number of intrusions.
Other prior art devices operate by requiring the intruder to physically contact the alarm, thereby completing a ground path that latches an electronic on/off switch. Another prior art device protects a glove compartment from intrusion by detecting a change of air pressure produced by suddenly opening the compartment door. Yet another prior art device is designed to protect a child from the contents of a medicine cabinet or household cleanser cupboard requiring two units as well as a magnetic switch to operate properly.
However, the prior art does not anticipate or suggest a device which is used to protect items included in a darkened enclosure, whereby an audible signal is produced for a predetermined period of time when the darkened enclosure is opened and the device is not disabled after a predetermined time delay and which would give the authorized user of the alarm a virtually instantaneous indication that the darkened enclosure was opened, even after the audible alarm ceases to produce a signal.